The proposed experiments will help to substantiate our previous results that describe the cell surface of exponentially growing Escherichia coli and Salmonella as a mosaic consisting of several hundred structurally distinct zones at which various membrane functions are localized. The model is based on our previous discoveries showing that 1) lytic events in the envelope take place at numerous areas randomly distributed over the cell surface, 2) outer and inner membranes are fused to each other at 200 to 400 sites, which are used as injection sites for a large variety of bacteriophages and which serve as anchoring points for F-pili and flagellae, 3) These zones appear to be involved in the insertion of newly synthesized lipopolysaccharides (O-antigen). We hypothesize that these adhesion sites are also involved in the synthesis and translocation of further cell surface components. We propose to study 1) the effect of changes in lipid composition on the structure and function of the envelope, 2) the sites of production, as well as the macromolecular composition and the function of the capsular polysaccharides as virus receptors, 3) The isolated unit elements of wild type polysaccharides as well as the molecules of filament-producing mutant strains to describe the adsorption mechanisms by which the enzymatically active virus can penetrate a thick capsular structure and position itself over a discrete adhesion site. We will be able to test our model in which for high efficiency of infection, a reduction in the degree of freedom of virus movement is obtained by guiding the virion along the receptor molecule toward its injection site. The combination of electron microscopic techniques with virological, immunological and biochemical methods will optimize the interpretation of our data and will aid us in the understanding of the structural and functional organization of cell surfaces in general.